Introduction: PJK is a prevalent problem following sagittal correction in adult spinal deformity (ASD). Changes in cervical alignment after PJK have not been investigated. This study investigates the changes in cervical alignment with novel radiographic parameters, CTPA and T1 Pelvic angle (TPA) (Figure 1), and established measures like C2-C7 plumbline (CPL) following PJK after thoracolumbar deformity correction.
Methods: Multicenter, retrospective, analysis of consecutive ASD patients undergoing 3CO with fusion to the pelvis with 1yr follow-up. PJK was defined as (>10° change in UIV and UIV+2 kyphosis). Patients were substratified into upper thoracic (UT) with UIV T6 and above and lower thoracic (LT) with UIV below T6.
Results: 166 ASD patients (mean=59.1yrs) were enrolled. PJK developed in 62 patients (37.3%). CTPA correlated strongly with CPL as a measure of cervical sagittal balance (r=0.916, p<0.001). Utilizing a linear regression analysis, a CTPA value of 3.6 was found to correspond to CPL of 4.0 cm. There were no significant differences in PJK patients and those without PJK (NPJK) in terms of preoperative thoracolumbar deformity (SVA or TPA), cervical alignment (CPL or CTPA), age, sex and BMI. PJK patients did not differ with NPJK by postoperative thoracolumbar alignment or magnitude of correction. For UT (n=86), patients with PJK at 1yr had larger CTPA (4.7 vs 3.6, p=0.008), CPL (4.83 vs 3.92 cm, p=0.03) and T1 Slope (T1S 26.9 vs 36.0 p=0.03) despite similar global corrections by SVA, TPA and PI-LL. This was not true for LT.
Conclusions: CTPA correlated strongly with C2PL as a measure of cervical sagittal balance. PJK was prevalent, developing in 37.3% of ASD patients undergoing thoracolumbar 3CO. Following 3CO, PJK patients with long fusions to the upper thoracic spine (UT) developed cervical sagittal deformities driven by an increase in T1S leading to an increase in their CPL and CTPA.
Patient Care: Improve our understanding of the potential impact on the cervical spine of proximal junction kyphosis in adults following surgery for thoracolumbar spinal deformity.
Learning Objectives: By the conclusion of this session, participants should be able to: (1) Understand how the novel measures of Cervical-Thoracic Pelvic Angle (CTPA) and T1 Pelvic angle (TPA) define the relative proportion of cervical and thoracolumbar deformities; (2) Appreciate the clinical role and application of the CTPA and TPA radiographic measures.